[SCEV] Improve code around constant TC (NFC) (llvm#133261)

Author: artagnon

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -8253,14 +8253,14 @@ unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L) {
     unsigned Multiple = getSmallConstantTripMultiple(L, ExitingBB);
     if (!Res)
       Res = Multiple;
-    Res = (unsigned)std::gcd(*Res, Multiple);
+    Res = std::gcd(*Res, Multiple);
   }
   return Res.value_or(1);
 }
 
 unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L,
                                                        const SCEV *ExitCount) {
-  if (ExitCount == getCouldNotCompute())
+  if (isa<SCEVCouldNotCompute>(ExitCount))
     return 1;
 
   // Get the trip count
@@ -8270,8 +8270,8 @@ unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L,
   // If a trip multiple is huge (>=2^32), the trip count is still divisible by
   // the greatest power of 2 divisor less than 2^32.
   return Multiple.getActiveBits() > 32
-             ? 1U << std::min((unsigned)31, Multiple.countTrailingZeros())
-             : (unsigned)Multiple.zextOrTrunc(32).getZExtValue();
+             ? 1U << std::min(31U, Multiple.countTrailingZeros())
+             : (unsigned)Multiple.getZExtValue();
 }
 
 /// Returns the largest constant divisor of the trip count of this loop as a